In modern cataract procedures, also called extracapsular cataract extraction, a hole is cut in the anterior capsular bag. This may be done using laser devices. Subsequently, the natural lens is removed. In the remaining parts of the capsular bag, in many suggested procedures an IOL is placed. The IOL more or less maintains its position in the empty bag.
Usually, an IOL is provided with haptics. These haptics extend radially from a lens of an IOL. After implanting an IOL, these haptics usually engage the inside circumference of the remaining capsular bag part in order to more or less keep the optics, for instance a lens, of the IOL centred and positioned in the capsular bag.
For improving fixation of the position of an IOL, many designs were proposed. U.S. Pat. No. 6,027,531 describes in its abstract “An intraocular lens for use in extracapsular cataract extraction has a haptic pa[r]t that surrounds the optical pa[r]t of the lens and further contains a groove of such shape to accommodate the anterior and posterior capsules of the lens bag after anterior capsulorhexis, extracapsular cataract extraction and posterior capsulorhexis. The lens is preferably inserted in a calibrated, circular and continuous combined anterior and posterior capsulorhexis, slightly smaller than the inner circumference of the groove as to induce a stretching of the rims of the capsular openings. This new approach is believed to prevent the appearance of secondary opacification of the capsules, allows a very stable fixation of the intraocular lens and ensures a tight separation between the anterior and posterior segment of the eye. This new principle of insertion is called the bag-in-the-lens technique, in contrast with the classical lens in-the-bag technique.”. Placement of this IOL requires skills and the capsular bag may get damaged. If after insertion the capsular bag ruptures, the IOL will not maintain its position.
In U.S. Pat. No. 6,881,225, an intraocular lens structure for reducing complications is described. According to the abstract, the intraocular lens structure comprises an optic, a support and a closing fixture. The closing fixture is a groove or a valley formed on the side portion of the optic of the intraocular lens. The valley is formed by the optic and a protrusion projecting posteriorly from the optic. The groove or the valley in the optic is made engaged with the posterior capsular opening generally over the entire circumference of the groove or the valley to close the opening of the posterior capsule. Like most of the current IOL structures, the structure also uses its haptics for keeping the structure in the capsular bag. The groove holds the posterior part of the capsular bag.
U.S. Pat. No. 5,171,320 describes in its abstract an intraocular lens system adapted to be implanted within a generally circular opening in an anterior wall of the capsular bag which normally contains the crystalline lens of an eye. The intraocular lens system includes a lens body having an annular groove which is formed in a peripheral portion thereof in a plane substantially perpendicular to an optical axis of the lens body. The lens body includes an optically effective portion located radially inside the annular groove, and an anterior lens portion and a posterior lens portion located on respective anterior and posterior sides of the annular groove. The intraocular lens system is secured in position within the circular opening such that an annular flap portion of the capsular bag which surrounds the circular opening is accommodated within the annular groove in the lens body.
EP2422746 discloses according to its abstract an intraocular implant for placement in the eye, e.g. as part of a cataract operation or crystalline lens extraction refractive operation, has at a peripheral portion of the implant a groove which engages with the lip of a single capsulotomy only formed in the lens capsule of the eye. The implant will normally be a lens, but may instead be a bung or plug for occluding an opening made in the capsule. The groove may be a continuous groove around the periphery of the implant, or there may be a series of individual spaced-apart grooves formed as projections protruding from the periphery. Instead of a single groove, a pair of axially spaced-apart grooves may be provided, which engage with respective capsulotomies formed in an anterior and a posterior part of the capsule. The posterior groove is preferably of a smaller mean diameter than the anterior groove. The description shows an embodiment with “a series of projections projecting from the circumference of the lens portion”, referring to very specific embodiments in the drawings.